This invention relates to a DC/AC converter for igniting and supplying a gas discharge lamp. The converter has two input terminals intended to be connected to a DC voltage source, said input terminals being connected together by means of a series arrangement which includes a load circuit, comprising at least the discharge lamp and an induction coil, and a first semiconductor switching element. The load circuit is shunted by a circuit comprising a second semiconductor switching element, said switching elements being rendered alternately conductive and non-conductive at a high frequency. A converter of this type is known from the U.S. PAT. NO. 4,647,820 (3/3/87).
This U.S. Patent describes a converter of the half-bridge type in which the lamp is shunted by a capacitor and a resistor having a positive temperature coefficient (PTC). A fairly large pre-heating current then flows through the electrodes, whereafter the lamp ignites readily. A current, though small, also flows continuously through the electrodes during the lamp operation in such a converter. This is detrimental to the efficiency of the converter.